倒计时防刷新的实现

<script type="text/javascript">  var maxtime;  if(window.name == ''){     maxtime = 60 * 60;  }else{    maxtime = window.name;  }  function CountDown(){    if(maxtime >= 0){      minutes = Math.floor(maxtime/60);      seconds = Math.floor(maxtime%60);      msg = "距离结束还有" + minutes + "分" + seconds + "秒";      document.all["timer"].innerHTML = msg;      if(maxtime == 5 * 60) alert('注意，还有5分钟!');      --maxtime;      window.name = maxtime;     }    else{      clearInterval(timer);      alert("时间到，结束!");    }  }  timer = setInterval("CountDown()", 1000);</script><div id="timer" style="color:red"></div>

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